1. Field of the Invention
For protecting pipes, intended for drilling oil or gas wells, pipe-end protectors are known by means of which the outer screw thread of said pipes can be protected against being damaged.
2. State of the Prior Art
Nearly all pipe-end protectors are provided with mechanical tensioning means included in a plastics body, by means of which the inner wall of said body can be clamped on a pipe-end by turning over a toggle handle. Such protectors operate satisfactorily as such, but have the objection that the clamping means have to be frequently readjusted for assuring a good clamping effect, and moreover said means can often be irrepairably damaged as a consequence of the occurring substantial thrust forces. The life of such protectors is, therefore, short, which is objectionable in view of the relatively high price thereof.
Pipe-end protectors have already been proposed which consist of a plastics body provided with a bore for accommodating the pipe-end to be protected, and having an interior cavity connecting, by means of a filling duct, with a filling connection which is accessible from the outside and is provided with a one-way valve, in order to clamp, by means of a pressure rise inside said cavity, the wall of the bore of said body against the pipe-end, a metal ring preventing the outward expansion of said body.
Since, when drilling, compressed air of about 0.9 MPa is always available, applying such protectors is very simple, and by pressing inwards the one-way valve or by actuating a separate depressurizing valve, the internal pressure can be quickly relieved for removing the protectors.
Said known pipe-end protectors have, however, such draw-backs that they have hardly been put into use. The metal protection rings are generally provided at the outside, and should have such a strength as to withstand transverse thrust loads, but in the case of very heavy thrusts such a ring can be indented, making the protector useless. In some protectors the filling connection is provided in the outer wall, so that on deformation of the ring the filling connection can be damaged, or leakage can occur in other ways. If the filling aperture is provided at the inner side of the body, there is a risk that when bumping against the end face, the filling duct will be sheared off by the shifting pipe, and leakage will occur. Apart from the fact that the protector is made useless thereby, the protector coming off will fall downwards if the pipe is situated at a substantial height, which is dangerous to the life of the drilling operators. Moreover there is the risk that by the protector coming off untimely, the screw thread of the pipe will be damaged.
This is the reason why said pipe-end protectors based on a correct and practical insight have not found the expected application, so that only the much less practical protectors with mechanical tensioning means are still in use.